'\" et
.TH PTHREAD_GETSCHEDPARAM "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.\"
.SH NAME
pthread_getschedparam,
pthread_setschedparam
\(em dynamic thread scheduling parameters access
(\fBREALTIME THREADS\fP)
.SH SYNOPSIS
.LP
.nf
#include <pthread.h>
.P
int pthread_getschedparam(pthread_t \fIthread\fP, int *restrict \fIpolicy\fP,
    struct sched_param *restrict \fIparam\fP);
int pthread_setschedparam(pthread_t \fIthread\fP, int \fIpolicy\fP,
    const struct sched_param *\fIparam\fP);
.fi
.SH DESCRIPTION
The
\fIpthread_getschedparam\fR()
and
\fIpthread_setschedparam\fR()
functions shall, respectively, get and set the scheduling policy and
parameters of individual threads within a multi-threaded process to be
retrieved and set. For SCHED_FIFO and SCHED_RR,
the only required member of the
.BR sched_param
structure is the priority
.IR sched_priority .
For SCHED_OTHER,
the affected scheduling parameters are implementation-defined.
.P
The
\fIpthread_getschedparam\fR()
function shall retrieve the scheduling policy and scheduling parameters
for the thread whose thread ID is given by
.IR thread
and shall store those values in
.IR policy
and
.IR param ,
respectively. The priority value returned from
\fIpthread_getschedparam\fR()
shall be the value specified by the most recent
\fIpthread_setschedparam\fR(),
\fIpthread_setschedprio\fR(),
or
\fIpthread_create\fR()
call affecting the target thread. It shall not reflect any temporary
adjustments to its priority as a result of any priority inheritance or
ceiling functions. The
\fIpthread_setschedparam\fR()
function shall set the scheduling policy and associated scheduling
parameters for the thread whose thread ID is given by
.IR thread
to the policy and associated parameters provided in
.IR policy
and
.IR param ,
respectively.
.P
The
.IR policy
parameter may have the value SCHED_OTHER, SCHED_FIFO, or SCHED_RR. The
scheduling parameters for the SCHED_OTHER policy are
implementation-defined. The SCHED_FIFO and SCHED_RR policies shall
have a single scheduling parameter,
.IR priority .
.P
If _POSIX_THREAD_SPORADIC_SERVER is defined, then the
.IR policy
argument may have the value SCHED_SPORADIC, with the exception for the
\fIpthread_setschedparam\fR()
function that if the scheduling policy was not SCHED_SPORADIC at the
time of the call, it is implementation-defined whether the function
is supported; in other words, the implementation need not allow the
application to dynamically change the scheduling policy to
SCHED_SPORADIC. The sporadic server scheduling policy has the
associated parameters
.IR sched_ss_low_priority ,
.IR sched_ss_repl_period ,
.IR sched_ss_init_budget ,
.IR sched_priority ,
and
.IR sched_ss_max_repl .
The specified
.IR sched_ss_repl_period
shall be greater than or equal to the specified
.IR sched_ss_init_budget
for the function to succeed; if it is not, then the function shall
fail. The value of
.IR sched_ss_max_repl
shall be within the inclusive range [1,\c
{SS_REPL_MAX}]
for the function to succeed; if not, the function shall fail.
It is unspecified whether the
.IR sched_ss_repl_period
and
.IR sched_ss_init_budget
values are stored as provided by this function or are rounded to
align with the resolution of the clock being used.
.P
If the
\fIpthread_setschedparam\fR()
function fails, the scheduling parameters shall not be changed
for the target thread.
.SH "RETURN VALUE"
If successful, the
\fIpthread_getschedparam\fR()
and
\fIpthread_setschedparam\fR()
functions shall return zero; otherwise, an error number shall be
returned to indicate the error.
.SH ERRORS
The
\fIpthread_setschedparam\fR()
function shall fail if:
.TP
.BR ENOTSUP
An attempt was made to set the policy or scheduling parameters to an
unsupported value.
.TP
.BR ENOTSUP
An attempt was made to dynamically change the scheduling policy to
SCHED_SPORADIC, and the implementation does not support this change.
.P
The
\fIpthread_setschedparam\fR()
function may fail if:
.TP
.BR EINVAL
The value specified by
.IR policy
or one of the scheduling parameters associated with the scheduling
policy
.IR policy
is invalid.
.TP
.BR EPERM
The caller does not have appropriate privileges to set either the
scheduling parameters or the scheduling policy of the specified
thread.
.TP
.BR EPERM
The implementation does not allow the application to modify
one of the parameters to the value specified.
.P
These functions shall not return an error code of
.BR [EINTR] .
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
None.
.SH RATIONALE
If an implementation detects use of a thread ID after the end of its
lifetime, it is recommended that the function should fail and report an
.BR [ESRCH] 
error.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "\fIpthread_setschedprio\fR\^(\|)",
.IR "\fIsched_getparam\fR\^(\|)",
.IR "\fIsched_getscheduler\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "\fB<pthread.h>\fP",
.IR "\fB<sched.h>\fP"
.\"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
.PP
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
